html {
    font-size: 10px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont,"Helvetia Neue","PingFang SC","Microsoft SC","Microsoft YaHei","Source Han Sans SC",
    "Noto Sans CJK","WenQuanYi Micro Hei",sans-serif;
    font-size: 16px;
    background-image: url(http://a1.jikexueyuan.com/home/201508/25/ccd7/55dbca0c40d6f.jpg);
    background: rgb(2,0,36);
    background: linear-gradient(0.25turn, #3f87a6, #ebf8e1, #f69d3c);
    background-repeat: no-repeat;
    background-position: 50% 50%;
}

h1 {
    font-weight: bolder;
    /* font-size: 1mm; */
    text-align: center;
    letter-spacing: -2px;
    /* text-decoration: underline; */
   }

section {
    font-size: 20px;
}

p {
    font-size: 1.5rem;
    /* font-size: large; */
    line-height: 1.5;
    text-indent: 2em;
}

.threeD { color:#fff; 
    text-shadow: 0 0 1px #999, 
    1px 1px 2px #888, 
    2px 2px 2px #777, 
    3px 3px 2px #666, 
    4px 4px 2px #555, 
    5px 5px 2px #333;
}

/* .demo3 {
    text-shadow: 0 0 5px #fff,
    0 0 10px #fff,
    0 0 15px #fff,
    0 0 40px #ff00de,
    0 0 70px #ff00de;  
} */

#text-prop div {
    width: 20vw;
    height: 20vh;
    background-color: #112233;
}

.box-demo{
    border: 4px white double;
    height: 100px;
    width: 100px;
    text-align: center;
    line-height: 100px;
    margin: 1rem 2rem 3rem 4rem;
    border-radius: 5px;
    box-shadow: 5px 5px 3px 0px rgb(2,0,36) ;
}

footer {
    border-top: 1px solid #ccc;
    margin-top: 5rem;
}

footer p {
    text-align: center;
    margin-top: 5rem;
}

footer {
    text-align: center;
    text-indent: 0;
    font-size: 12px;
}

footer span {
    margin: 0 2rem;
}

